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boost::unary_traits
by Matthias Kaeppler 07 Mar '05

07 Mar '05

Hello, I have written an adaptor for functions and function objects which allows to invoke operations on the pointees when working on a collection of pointers. For example, it allows to sort a list of pointers by a predicate applying to the pointees. To make it work with normal functions and functors, I utilized boost::unary_traits and boost::binary_traits. This is the class template for the unary version: template< typename Operation > class indirecter_unary : public std::unary_function< typename boost::unary_traits<Operation>::argument_type, typename boost::unary_traits<Operation>::result_type > { typedef typename boost::unary_traits<Operation>::argument_type arg_type; typedef typename boost::unary_traits<Operation>::param_type param_type; typedef typename boost::unary_traits<Operation>::result_type result_type; typedef typename boost::unary_traits<Operation>::function_type function_type; function_type op_; public: explicit indirecter_unary( param_type op ): op_(op) {} result_type operator() (arg_type *arg) const { return op_(*arg); } }; Now, the problem arises when I pass a function which takes references. Like this: bool pred( int& a ) { //... } indirecter_unary< bool ()(int&) > fctor(pred); ext::indirecter_unary<bool ()(int&)>': code/FileBrowser.cpp:90: instantiated from here code/ext/indirect.hpp:80: error: forming pointer to reference type `int&' Line 80 is the line where operator() is defined. The error message indicates that argument_type is obviously not correct in this context. I thought the boost traits would take care of the right argument types? Am I missing something? -- Matthias Kaeppler

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Safe downcast of a shared_ptr?
by steve ahlgren 07 Mar '05

07 Mar '05

Hello : Is there safe/easy way to downcast shared pointers? ie boost::shared_ptr< Derived_Type > dPtr = [appropriate_method_here] ( base_ptr ); Thanks in advance; Steve a.

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[regex] Is there any function to know where the input fails to match a regex?
by jordi 07 Mar '05

07 Mar '05

Hello, Maybe my question is a silly question but I have a recurrent problem and maybe there is an easy solution: I need to create a lot of regex expressions to match several Unix command outputs. Usually, my firsts regex definitions are wrong and they don't match, so when the match fails I would like to know where the "problem" is (more or less) in order to change the regular expression. For example: Input text: "123 hello abc" My first wrong Regex: "(\d)+\s+(\w)+\s+(\d)+" If I try to match this input against the regex using regex_search with the boost::match_continuous flag I only have the false value returned by the function but it doesn't help me to know that the "123 hello" matched the regex because the problem starts at "abc" trying to match "(\d)+". I can simulate what I need checking subexpressions adding every iteration a new "sub-regex" and stopping when the match fails (I do it manually, changing the regex). With my undefined funtion I would obtain: - Input text:"123 hello abc" - Latest rigth Regular expression: "(\d)+\s+(\w)+\s+" Matches: "123 hello " - First wrong regex: "(\d)+\s+(\w)+\s+(\d)+" does not match. -> So, "(\d)+" does not match "abc" I understand that usually this is not as easy as I write in my simple example because of the power of regular expressions but I think a function like that would improve a lot the error reporting capabilities. Is there any way to do what I need or I must to write my own check function? Best regards, Jordi

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Borland compiler error E2437
by Roman Morokutti 07 Mar '05

07 Mar '05

Hi, I am not able to compile function_base.hpp at lines 595(55), 607(55), 616(55), 625(55). Error E2437 D:\boost\boost_1_32_0\boost/function/function_base.hpp 598(55): 'typename' should be followed by a qualified, dependent type name Does anyone know a workaround for this? Greetings Roman

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Problems using boost-regex after being compiled as non root.
by Javier-Elias Vasquez-Vivas 07 Mar '05

07 Mar '05

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RE: [Boost-users] Re: Q: boost::format : can formatting variablea rguments lists be done ?
by Foster, Gareth 07 Mar '05

07 Mar '05

Could you do Logger<DBG> MyLogger; MyLogger.print(); ? -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Dan Dimerman Sent: 22 December 2004 13:03 To: boost-users(a)lists.boost.org Subject: [Boost-users] Re: Q: boost::format : can formatting variablearguments lists be done ? Richard Howells wrote: > Vladimir is right. > > You've seen the problems and crashes that leaving type checking to the > programmer causes. You need the compiler to do the checking for you. > > I suggest using the same kind of scheme as the iostreams library. You might /.../ > ...it will be (mostly) type safe - the type dangerous stuff is isolated to > one place per output type - and you can extend it as you go. You'll likely > need extra formatting stuff and that's where boost::format may help you. > I was thinking about something like: MyLogger::print( const boost::format& f ) and since all format's operator %() return a boost::format, I could with this single function reap all the types handled by it at once. I use a function rather than the operator << because they are actually template functions, with the parameter being the severity. So for _DEBUG versions, the MyLogger::print< DBG >() function instantiates to a proper call to print, while in _RELEASE versions it instantiates to an empty function. I just didn't see a clean way to do this with operators. Dan _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Re: Logo Contest: Send In Your votes!
by Joel de Guzman 07 Mar '05

07 Mar '05

Hi, I have to apologize to Mike Mangone. For some reason, I missed his submission dated Feb 16. For those who voted already, please check out his entry (no. 99). If you find his entry compelling, I am willing to make corrections to my tally if any of you wish to resend your votes. Again, pardon me for this slip. http://boost.org/more/logo_contest.htm Send your votes to: boost.logo.contest(a)gmail.com Kind Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net

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Serialization library and memory issues
by Mike Lapshin 06 Mar '05

06 Mar '05

Hello Boost-users, I'm trying to save a simple class to xml_woarchive: class StringContainer { std::map<std::string, std::wstring> mStrings; friend class boost::serialization::access; template<class TArchive> void serialize(TArchive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(mStrings); } public: typedef std::map<std::string, std::wstring> StringMap; StringContainer() {} ~StringContainer() {} void addString (const std::string& id, const std::wstring& str); bool isStringExists (const std::string& id) const; const std::wstring& getString(const std::string& id) const; void removeString (const std::string& id); }; // somewhere in main code: StringContainer sc; sc.addString("fps.profilerfl", L"FPS: "); sc.addString("triangles.profilerfl", L"Triangles: "); std::wofstream outfs("strings.xml"); assert(outfs.good()); boost::archive::xml_woarchive oa(outfs); oa << BOOST_SERIALIZATION_NVP(sc); But somewhere after it (i think it is in xml_woarchive destructor) my program falls with "Debug Assertion Failed" (I'm using VC7.1) message: HEAP[test.exe]: Invalid Address specified to RtlValidateHeap( 011B0000, 011F29E8 ) Unhandled exception at 0x77f767cd in test.exe: User breakpoint. By the way, xml file writes as expected: <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="3"> <sc class_id="0" tracking_level="0" version="0"> <mStrings class_id="1" tracking_level="0" version="0"> <count>2</count> <item class_id="2" tracking_level="0" version="0"> <first>fps.profilerfl</first> <second>FPS: </second> </item> <item> <first>triangles.profilerfl</first> <second>Triangles: </second> </item> </mStrings> </sc> </boost_serialization> What i'm doing incorrectly? -- Mike Lapshin

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boost::threads Am I on the right track?
by The Grumpiest Man You Know 06 Mar '05

06 Mar '05

I've had a minor epiphany, or at least I think so, in use of boost::threads. I would be very grateful if someone who actually knew something about C++ and boost's threads support would glance at the attached code. Any comment would be appreciated especially if there's sign that I'm horribly misusing the scraps I've picked up. I have to say that once I stopped trying to relate the pthreads C API to the bits of the docs I could understand my reaction was, "Sweet!" I think the way the threading and locking "disappear" is ... really elegant. Thanks very much for your time and again if I'm OT please tell me where to go, even if it is to hell. :) ------------ #include <iostream> #include <vector> #include <queue> #include <boost/thread/thread.hpp> #include <boost/function.hpp> using namespace std; using namespace boost; mutex::mutex io; struct Throttle { Throttle(void (*fn)(), int svcQLen = 5) : population(1), load(0), acceptable(svcQLen), service(fn) { }; ~Throttle() { cout << "load is " << load << endl; cout << "Population " << population << endl; } void itsBusy() { mutex::scoped_lock myPermission(use); if (++load > acceptable) { workers.create_thread(service); population++; load = 0; }; }; void observe() { workers.join_all(); }; private: mutex use; int population; int load; int acceptable; void (*service)(); thread_group workers; }; template <class T> struct RequestQ : public queue<T> { typedef T value_type; typedef queue<T> cBase; bool empty() { mutex::scoped_lock permit(use); return cBase::empty(); } value_type pop() { mutex::scoped_lock permit(use); value_type it = cBase::front(); cBase::pop(); mutex::scoped_lock doing(io); cout << "Q -> " << it << endl; return it; } void extend(unsigned int by) { mutex::scoped_lock permit(use); value_type next; if (cBase::empty()) { next = 0; // Yeah, assumes integral type conversion } else { next = cBase::back(); } while(by--) { push(*new value_type(++next)); } } private: void push(const value_type& it) { mutex::scoped_lock doing(io); cout << "Q <- " << it << endl; cBase::push(it); } mutex use; }; /* * We have to initialise this before creating any threads but that's * OK 'cos this IS the way we'll create threads. */ Throttle *manager; RequestQ<int> jobs; void go() { for(int range = 0; !jobs.empty(); range = 0) { int mine = jobs.pop(); if (!jobs.empty()) { manager->itsBusy(); } { mutex::scoped_lock doing(io); bool term = false; if (!(mine % 3)) { cout << "fizz "; range=1; term = true; } if (!(mine % 5)) { cout << "buzz "; range += 1; term = true; } if (!(mine % 7)) { cout << "pop! "; range = 0; term = true; } if (!(mine % 11)) { cout << "puff"; range = 2 * (range + 1); term = true; } if (term) { cout <<endl; } } if (range) { jobs.extend(range); sleep(range); } } } int main(int argc, char **argv) { manager = new Throttle(&go); jobs.extend(argc * 10); go(); manager->observe(); delete manager; } -- Blue Skies

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boost serialization linking problems with certain binutils
by Daniel Goller 05 Mar '05

05 Mar '05

hi, im looking for feedback as well as a possible fix for boost serialization with binutils >2.15.90.0.* with binutils 2.15.90.0.* the boost serialization demo links properly with newer (stable on gentoo) binutils we see a myriad of gnu linkonce errors from the linker so i would like to know if anyone here can link the serialization demo.cpp with 2.15.92.* binutils if yes on which distro and the exact version of the binutils better yet, i would like to know how i can build boost serialization also as a shared lib, as none of the other libs which exist in shared and static version have problems with linking with 2.15.92.* bintuils thank you in advance for your input and help Daniel

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